Fixation instrument for treating a bone fracture

ABSTRACT

A fixation instrument for treating a bone fracture including a bone screw and a nail, wherein the bone screw extends through an opening in the head or proximal end of the nail. A movable insert is disposed within a chamber located at the proximal end of the nail. The insert engages the bone screw to prevent rotation thereof once the bone screw is placed in position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/552,229, filed Mar. 11, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a fixation instrument fortreating bone fractures. More specifically, a nail and bone screwcombination used to treat a fracture of the femur includingtrochanteric, intertrochanteric and femoral neck fractures.

2. Background of the Invention

Orthopedic fixation systems used for stabilizing a fracture ofteninclude an internal fixation device, typically an elongated implant suchas a nail, screw or pin, inserted into the intramedullary canal of thebone to stabilize the fracture and promote healing. Such fixationsystems are often used with a fracture of the femur. The femur generallyincludes an elongated shaft, a ball shaped head that fits into the hipsocket and a neck connecting the ball to the shaft. The shaft alsoincludes a greater trochanter and a lesser trochanter.

Typically, the nail is inserted in the marrow canal of the bone and ispositioned to span the fracture. Nails are also used to treat fracturesof the neck, head, intertrochanter, subtrochanteric, pathologic andcertain ipsilateral shaft and neck fractures of the femur. For example,if the neck of the femur sustains a fracture a bone screw insertedthrough an aperture in the nail spans the fracture and threadablyengages the femoral head.

Typically, the aperture in the end of the nail is a smooth bore in whichthe bone screw rotates as it threadably engages the femoral head. Oncethe bone screw is suitably tightened, it is left in place during thehealing process. Bone screw migration is one problem that may occurduring the healing process. Specifically, during loading or movement ofthe femur, the bone screw may migrate or loosen, thus creating a risk offailure at the fracture. Accordingly, there is in need for a fixationinstrument that resists bone screw migration and rotation.

SUMMARY OF THE INVENTION

Accordingly, the present invention is a fixation instrument including abone nail and bone screw combination for use in repairing a bonefracture. The bone nail extends within the shaft portion of a bone suchas a femur. An opening in the head or proximal end of the nail receivesa bone screw that, in the case of a femoral neck fracture, extends intothe femoral head.

In accordance with an aspect of the present invention, a locking insertdisposed within the nail engages the bone screw and prevents rotationthereof. Further areas of applicability of the present invention willbecome apparent from the detailed description provided hereinafter. Itshould be understood that the detailed description and specificexamples, while indicating the preferred embodiment of the invention,are intended for purposes of illustration only and are not intended tolimit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic front view of a fixation instrument accordingto the present invention shown implanted within a femur.

FIG. 2 is an enlarged front view of the proximal end of the fixationinstrument according to the present invention with portions removed forclarity and illustration.

FIG. 3 is a cross-sectional view of the bone screw shown in FIG. 2 takenalong lines 3-3.

FIGS. 4A-4E are various views of an insert for use with the fixationinstrument according to the present invention.

FIG. 5 is a side view of a locking ring for use with the fixationinstrument according to the present invention.

FIG. 6 is a side view of a cap for use with the fixation instrumentaccording to the present invention.

FIG. 7 is a front view of an alternative embodiment of a fixationinstrument according to the present invention with portions removed forclarity and illustration.

FIGS. 8A-8D are various views of an alternative embodiment of an insertfor use with the fixation instrument according to the alternativeembodiment of FIG. 7.

FIG. 9 is a front view of an additional alternative embodiment of afixation instrument according to the present invention with portionsremoved for clarity and illustration.

FIGS. 10A-10D are various views of the additional alternative embodimentof an insert for use with the fixation instrument according to thealternative embodiment of FIG. 9.

FIG. 11 is a side view of a cap for use with the fixation instrumentaccording to the alternative embodiment of FIG. 9.

FIG. 12 is a front view of a further alternative embodiment of afixation instrument according to the present invention.

FIG. 13 is a front view, with portions removed for clarity, of the capand insert assembly used in connection with the fixation instrumentaccording to the embodiment of FIG. 12.

FIG. 14 is a side view of the further alternative embodiment of thefixation instrument shown in FIG. 12.

FIG. 15 is a side view of the cap and insert assembly shown in FIG. 12used in connection with the fixation instrument according to theembodiment of FIG. 12, with FIG. 15A being a bottom view of the insertassembly of FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a fixation instrument, seen generally at 20, according toone embodiment of the present invention placed in an assembled conditionwithin a bone 10, illustrated here as a femur. The fixation instrument20 includes a nail member 22 formed of a metallic alloy, such as atitanium alloy. The nail member 22 includes a distal end 18 and aproximal end 24. The distal end 18 typically includes at least onetransverse aperture that receives a bone screw 16 used to fix the distalend 18 of the nail member 22 in place in the bone 10. The proximal end24 includes a trailing or rear edge 26.

Turning now to FIGS. 2-6, a passageway 28 extends longitudinally throughthe nail member 22 between the proximal end 24 and the distal end 18.The passageway 28 receives insertion and extraction instrumentation,such as a guide wire (not shown), used to position the nail member 22within the bone 10. Typically, the distal end 18 of the nail member 22is inserted into the bone 10 first and follows the path of the guidewire.

The proximal end 24 includes an aperture 30 extending through theproximal end 24 in a direction that is typically angled with respect tothe longitudinal axis 25 of the nail member 22. A bone screw 32 having athreaded portion 34 on one end thereof extends through the aperture 30such that the threaded portion 34 engages the femoral head 12 forsliding compression of a femoral neck 14 or intratrochanteric fracture.

An insert 36 having a distal end 38 and a proximal end 40 is disposedwithin a chamber 42 located in the proximal end 24 of the nail member22. The insert 36 further has a pair of tabs or guide/locating members44 that extend radially outward from the body of the insert 36. The tabsor guide/locating members 44 cooperate with a pair of grooves orchannels 46 that extend longitudinally along the sidewalls 48 of thechamber 42. The proximal end 24 of the nail member 22 includes anopening 50 at the trailing or rear edge 26 of the nail member 22. Theopening 50 provides access to the chamber 42.

The insert 36 further includes a lower surface 52 having a pair oflocking projections 54 extending longitudinally downward/outward fromthe lower surface 52. The insert 36 is placed in the chamber 42 throughthe opening 50, such that the tabs or guide/locating members 44 arereceived in the grooves or channels 46 located in the sidewalls 48 ofthe chamber 42. Accordingly, the insert 36 is slidably received andprevented from rotating in the chamber 42. The lower surface 52 of theinsert 36 extends or is oriented at an angle that is substantially thesame as the angle of the aperture 30 extending through the proximal end24 of the nail member 22. As set forth below, the insert 36 engages thebone screw 32 disposed in the aperture 30 in the nail member 22.

The bone screw 32 further includes a plurality of longitudinallyextending grooves 56 located on the outer surface 58 of the bone screw32. The grooves 56 are of a size and shape that are complementary to thelocking projections 54 located on the lower surface 52 of the insert 36.As seen in FIG. 2, when the insert 36 travels longitudinally in thechamber 42 it reaches a point wherein the lower surface 52 and lockingprojections 54 of the insert 36 are adjacent the bone screw 32. Sincethe purpose of the locking projections 54 is to engage the grooves 56 tosecure and prevent rotation of the bone screw 32 it may be necessary torotate the bone screw 32 slightly to align the grooves 56 of the bonescrew 32 with the locking projections 54 of the insert 36. Once properlyaligned, the insert 36 is driven further within or into the chamber 42until the lower surface 52 of the insert 36 engages the outer surface 58of the bone screw 32 and the locking projections 54 of the insert 36extend into the grooves 56 of the bone screw 32.

A locking ring 60 controls the position of the insert 36 within thechamber 42. The locking ring 60 has a plurality of threads 62 disposedabout the outer surface of the locking ring 60. The locking ring 60threadably engages a plurality of threads 64 disposed on the sidewalls48 of the chamber 42. As shown in FIG. 5, the locking ring 60 includes apost portion 66 located on or forming a portion of the lower surface 68of the locking ring 60. The post portion 66 further includes an inwardlyprojecting finger 70. The post portion 66 may be formed as an annularmember that extends all the way around the lower surface 68 or it may beformed as a plurality of individual post members spaced about the lowersurface 68 of the locking ring 60.

The inwardly projecting finger 70 cooperates with a retaining member 72formed on the upper surface 74 of the proximal end 40 of the insert 36.The retaining member 72 further includes an annular member 76 having anoutwardly extending lip 78. Accordingly, the locking ring 60 is placedon or attached to the insert 36 using a snap or press fit arrangement.Specifically, the locking ring 60 is placed on the upper surface 74 ofthe insert 36 and a sufficient force is exerted on the locking ring 60to deflect the inwardly projecting fingers 70 and correspondingly thepost portion 66 outward over the annular member 76. Upon clearing theannular member 76, the fingers 70 snap back into place whereby theyengage the underside of the lip 78 and rotatably secure the locking ring60 to the insert 36. It should be understood that such an arrangementenables the locking ring 60 to rotate about the longitudinal axis 37 ofthe insert 36 while remaining attached to the insert 36.

The locking ring 60 has an aperture or opening 80 having a hexagonalshape that functions as a drive portion of the locking ring 60.Accordingly, a suitable tool, such as a T-handle hexagonal wrench, maybe inserted into the opening 80 to rotate or turn the locking ring 60.This arrangement enables the insert 36 to be placed in the chamber 42prior to the nail member 22 being inserted into the bone. Otherconfigurations may function or comprise the drive portion, includingputting a slot in the upper surface of the locking ring 60 that receivesa driving tool such as a screwdriver.

The insert 36 is placed within the chamber 42 such that the tabs orguide/locating members 44 engage the grooves/channels 46 located in thesidewalls 48 of the chamber 42. Since the overall outer diameter of theinsert 36 is less than the inner diameter of the threads 64 in thesidewalls 48 of the chamber 42, the insert 36 slides freely in thelongitudinal direction and is constrained against rotation by the tabsor guide/locating members 44. As shown, the locking ring 60 is rotatablyattached to the insert 36. Accordingly, when the threads 62 on thelocking ring 60 engage the threads 64 in the sidewall 48 of the chamber42 and when the locking ring 60 is rotated by a suitable tool, thelocking ring 60 moves the insert 36 longitudinally within the chamber42. As set forth above, the insert 36 and locking ring 60 combination isplaced within the chamber 42 prior to inserting or installing the nailmember 22 in the bone 10.

In use, once the nail member 22 is installed in the bone 10, the bonescrew 32 is placed in and extends through the aperture 30 whereby itengages the femoral head 12. After tightening the bone screw 32 tocompress the fracture, a suitable tool engages and rotates the lockingring 60 to move the insert 36 downwardly within the chamber 42 until thelocking projections 54 engage the grooves 56 on the outer surface 58 ofthe bone screw 32. If necessary, it may be required to rotate the bonescrew 32 slightly in order to have the locking projections 54 line upwith the grooves 56. Once the insert 36 and bone screw 32 are properlyaligned, tightening the locking ring 60 maintains engagement between thelocking projections 54 and the grooves 56 and prevents rotation of thebone screw 32.

After tightening the locking ring 60, the opening 50 at the trailing orrear edge 26 of the nail member 22 is closed by a cap 82 threadablyreceived in the chamber 42. The cap 82 includes a threaded post 84, thethreads being of a suitable size and configuration to engage the threads64 located in the sidewall 48 of the chamber 42. The cap 82 furtherincludes a socket 85 suitable for receiving a driving tool to rotate andsecure the cap 82 in the opening 50.

It should be understood that the insert 36 and locking ring 60 both havelongitudinal passageways 86, 88 that allow the nail member 22 to beinserted within the bone 10 and follow a guide wire (not shown), withboth the insert 36 and locking ring 60 installed or positioned withinthe chamber 42 of the nail member 22. Accordingly, the present inventionenables the insert 36 to be pre-positioned or placed in the nail member22 prior to installation, thus eliminating the need and difficulty ofhaving to thread the insert 36 in place after the nail member 22 isplaced within the bone 10.

FIGS. 7-8 disclose an additional embodiment of a fixation instrument 20,according to the present invention. Specifically, the lower surface 110of the insert 36 has an arcuate surface having a shape complementary tothe outer diameter of the bone screw 32. This embodiment does not usethe locking projections of the previous embodiment, nor does the bonescrew 32 have longitudinal grooves contained therein. The arcuate shapeof the lower surface 110 creates a greater amount of surface area of theinsert 36 that contacts the outer surface 58 of the bone screw 32. Thus,tightening the locking ring 60 provides a sufficient force to createfriction fit between the insert 36 and the bone screw 32 that preventsrotation of the bone screw 32 within the aperture 30 of the nail member22.

FIG. 8A further illustrates an alternative embodiment of a rotatableconnection between the locking ring 60 and the insert 36. As showntherein, the locking ring 60 includes a downwardly projecting finger 120having an inwardly beveled surface 122 and a lip 124. The insert 36includes a inwardly extending flange 126. As with the previousembodiment, the locking ring 60 is rotatably attached to the insert 36using a snap or press fit arrangement. Specifically, applying a force tothe locking ring 60 causes the beveled surface 122 of the downwardlyprojecting finger 120 to engage the inwardly extending flange 126 anddeflect the finger 120 radially inward until the lip 124 of the lockingfinger 120 clears the flange 126 and whereby the locking finger 120snaps outwardly and the lip 124 engages the underside of the flange 126to rotatably secure the locking ring 60 to the insert 36.

FIGS. 9-11 show an alternative embodiment of a fixation instrument 20according to the present invention. As shown in FIG. 9, the proximal end24 of the nail member 22 has an additional aperture 90 for receiving asecond bone screw 92. As set forth in the previous embodiment, theinsert 94 includes tabs or guide/locating members 96 that are receivedin the grooves/channels 46 located on the sidewalls 48 of the chamber 42whereby the insert 94 is slidably fit within the chamber 42. The insert94 has an arcuate lower surface 97 having a degree of curvaturecorresponding to the radius of the bone screw 32. Accordingly, as setforth above, rotating the locking ring 100 causes the arcuate lowersurface 97 of the insert 36 to engage the outer surface 58 of the bonescrew 32 to prevent rotation of the bone screw 32 within the aperture 30of the nail member 22. The insert 94 also includes an aperture 98extending at an angle with respect to the longitudinal axis of theinsert 94 for receiving the second bone screw 92. The aperture 98 iselongated in the longitudinal direction to allow for travel of theinsert 36 within the passageway 28 without engaging the second bonescrew 92.

A cap 102 including an elongated tab or locking projection 104 is usedto secure the second bone screw 92. When the cap 102 is inserted intothe opening 50 on the trailing or rear edge 26 of the nail member 22,the elongated tab or locking projection 104 engages the second bonescrew 92 to prevent rotation thereof via a frictional fit. In addition,the elongated tab or locking projection 104 may include and engagementportion which sits within a groove located on the second bone screw 92,as with the previous embodiments, to further prevent rotation of thesecond bone screw 92. This arrangement prevents rotation of both thefirst and second bone screws 32, 92 with respect to the nail member 22.

FIGS. 12-15 show a further alternative embodiment of a fixationinstrument 20 according to the present invention, wherein the insert 36has a lower surface formed of a pair of downwardly extending fingers114. Each of the downwardly extending fingers 114 has an arcuateengagement surface 116 having a curvature or radius of curvaturecomplementary to the diameter of the bone screw 32. The arcuateengagement surfaces 116 form the lower or contact surface of the insert36. Accordingly, each of the fingers 114 engages the bone screw 32 tosecure or prevent rotation of the bone screw 32 within the aperture 30.The insert 36 is positioned in and secured within the chamber 42 in amanner similar to the first embodiment. As with the previousembodiments, the locking ring 60 is used to position and secure theinsert 36 whereby the arcuate engagement surfaces 116 of the fingers 114engage the bone screw 32 and prevent rotation thereof.

It should be understood that the mounting relationship between thelocking ring 60 and the insert 36 is one that enables the locking ring60 to turn or rotate freely on the insert 36. In the case of thedisclosed embodiments, the insert 36 travels longitudinally within thegrooves or channels 46 located in the sidewalls 48 of the chamber 42.Thus, the apparatus and corresponding components forming the snap orpress fit mounting relationship between the locking ring 60 and theinsert 36, as shown in the disclosed embodiments, including the inwardlyprojecting finger and lip on the annular member, may be positioned oneither the respective locking ring 60 or insert 36; i.e., the finger maybe on the insert 36 or the locking ring 60 as long as the complementarycomponent, the lip, is on the corresponding member.

Thus, it will be seen that the objects of the invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing specific embodiments have been shown and described for thepurposes of illustrating the functional and structural principles of theinvention and is subject to change without departure from suchprinciples. Therefore, this invention includes all modificationsencompassed within the scope of the following claims.

1. A fixation instrument for treating a bone fracture comprising: a nailmember, said nail member having a longitudinal axis, a distal end and aproximal end, said proximal end having an aperture extendingtherethrough and said nail member having a chamber located in saidproximal end; an insert having a longitudinal axis, said insertpositioned and constrained against rotation about said longitudinal axisof said insert within said chamber; a bone screw, having a threadedportion, said bone screw extending through said aperture; a locking ringreceived in said chamber and engaging said insert, said locking ringoperative to secure said insert within said chamber; and said inserthaving a distal end and a proximal end, a concave lower surface locatedat said distal end of said insert, said concave lower surface being thatportion of the insert spaced farthest from the proximal end and engaginga convex surface of said bone screw, said convex surface complementaryto said concave lower surface of said insert, when said bone screwextends through said aperture.
 2. A fixation instrument for treating abone fracture as set forth in claim 1 wherein said nail member has anopening adjacent a rear edge of said nail member to provide access tosaid chamber.
 3. A fixation instrument for treating a bone fracture asset forth in claim 1 including said chamber having a plurality ofthreads located on an inner surface thereof; said locking ring having aplurality of threads located on an outer surface thereof, said threadson said locking ring complementary to said threads on said inner surfaceof said chamber; and said locking ring having a drive portion, whereby asuitable tool engages said drive portion and is used to move saidlocking ring.
 4. A fixation instrument for treating a bone fracture asset forth in claim 1 including said concave lower surface having a shapecomplementary to an outer diameter of said bone screw.
 5. A fixationinstrument for treating a bone fracture as set forth in claim 4including said aperture extending through said nail member at an anglewith respect to the longitudinal axis of said nail member; and saidlower surface extending at an angle substantially the same as the angleof said aperture.
 6. A fixation instrument for treating a bone fracturecomprising: a nail member, said nail member having a longitudinal axis,a distal end and a proximal end, said proximal end having an apertureextending therethrough and said nail member having a chamber located insaid proximal end; an insert adapted to be positioned within saidchamber and having a lower surface, said lower surface operative tocontact a bone screw extending through said aperture; a locking ringreceived in said chamber and engaging said insert, said locking ringoperative to secure said insert within said chamber; a lockingprojection located on said lower surface of said insert; and said bonescrew having a longitudinally axis and having a plurality oflongitudinal extending grooves, said grooves extending substantiallyparallel to said longitudinal axis of said bone screw on an outersurface of said bone screw wherein said locking projection is located inone of said grooves when said lower surface contacts said bone screw. 7.A fixation instrument for treating a bone fracture as set forth in claim6 including said aperture extending through said nail member at an anglewith respect to the longitudinal axis of said nail member; and saidlower surface extending at an angle substantially the same as the angleof said aperture.
 8. A fixation instrument for treating a bone fractureas set forth in claim 6 wherein each of said insert and said lockingring have longitudinal passageways extending therethrough, wherein saidlongitudinal passageway extending through said insert terminates at saidlower surface.
 9. A fixation instrument for treating a bone fracture asset forth in claim 6 wherein said locking ring is rotatably connected tosaid insert.
 10. A fixation instrument for treating a bone fracture asset forth in claim 9 wherein said locking ring includes a post portionhaving an inwardly projecting finger; and said insert having a retainingmember located on a distal end thereof, said retaining member includingan outwardly extending lip wherein said locking finger engages said lipto rotatably secure said locking ring to said insert.
 11. A fixationinstrument for treating a bone fracture as set forth in claim 6including a cap, said cap operative to close said opening located atsaid rear edge of said nail member.
 12. A fixation instrument fortreating a bone fracture as set forth in claim 6 wherein said lowersurface is an arcuate surface.
 13. A fixation instrument for treating abone fracture comprising: a nail member, said nail member having alongitudinal axis, a distal end and a proximal end, said proximal endhaving an aperture extending therethrough at an angle with respect tothe longitudinal axis of said nail member and said nail member having achamber located in said proximal end; a bone screw; an insert adapted tobe positioned within said chamber, said insert having a proximal end anda distal end, said distal end terminating at said lower surface, saidlower surface extending at an angle substantially the same as the angleof said aperture extending through said nail member and engaging saidbone screw when said bone screw extends through said aperture; a lockingring received in said chamber and engaging said insert, said lockingring operative to secure said insert within said chamber; said nailmember having a second aperture extending therethrough for receiving abone screw; and said insert having an aperture therein extending at anangle with respect to a longitudinal axis of said insert, said anglesubstantially the same as the angle of said second aperture extendingthrough said nail member, said aperture for receiving a bone screw. 14.A fixation instrument for treating a bone fracture as set forth in claim13 wherein said insert includes a longitudinal passageway extendingthrough said insert; said locking ring having a longitudinal passagewayextending through said locking ring; and a cap, said cap having anelongated locking projection, said elongated locking projectionextending through said passageway in said locking ring and into saidpassageway in said insert, said elongated locking projection operativeto engage a bone screw extending through said aperture in said insert.15. A fixation instrument for treating a bone fracture as set forth inclaim 14 wherein said locking ring is rotatably connected to saidinsert.
 16. A fixation instrument for treating a bone fracturecomprising: a nail member, said nail member having a longitudinal axis,a distal end and a proximal end, said proximal end having an apertureextending therethrough at an angle with respect to said longitudinalaxis, said nail member having a chamber located in said proximal end,said chamber having a plurality of threads located on an inner surfacethereof and at least one groove located in said chamber; an inserthaving a distal end and a proximal end adapted to be positioned withinsaid chamber, said insert having at least one locating member, saidlocating member cooperating with said groove located in said chamber,said insert having a concave lower surface forming said distal end, saiddistal end and correspondingly said concave lower surface operative toengage a convex surface of said bone screw when said bone screw extendsthrough said aperture; and a locking ring received in said chamber andengaging said insert, said locking ring having a plurality of threadslocated on an outer surface thereof, said threads complementary to saidthreads on said inner surface of said chamber wherein said locking ringis threadably received in said chamber, said locking ring operative tosecure said insert within said chamber.
 17. A fixation instrument fortreating a bone fracture as set forth in claim 16 wherein said lockingring is rotatably connected to said insert.
 18. A fixation instrumentfor treating a bone fracture as set forth in claim 16 wherein saidinsert and said locking ring each have a longitudinal passagewayextending therethrough.
 19. A fixation instrument for treating a bonefracture comprising: a nail member, said nail member having alongitudinal axis, a distal end and a proximal end, said proximal endhaving a plurality of apertures extending therethrough, each apertureextending at an angle with respect to said longitudinal axis and saidnail member having a chamber located in said proximal end, said chamberhaving a plurality of threads located on an inner surface thereof and atleast one groove located in said chamber; an insert adapted to bepositioned within said chamber, said insert having at least one locatingmember, said locating member cooperating with said groove located insaid chamber, said insert including an aperture extending therethroughat an angle with respect to a longitudinal axis of said insert andincluding a longitudinal passageway extending therethrough, said inserthaving a lower surface, said longitudinal passageway extending to saidlower surface, said lower surface operative to engage a bone screwextending through said aperture; a locking ring received in said chamberand engaging said insert, said locking ring having a plurality ofthreads located on an outer surface thereof, said threads complementaryto said threads on said inner surface of said chamber wherein saidlocking ring is threadably received in said chamber, said locking ringhaving a longitudinal passageway therethrough and a drive portionsuitable to receive a tool used to rotate said locking ring in saidchamber, said locking ring operative to secure said insert within saidchamber; and a cap, said cap threadably received in said chamber andhaving an elongated locking projection, said elongated lockingprojection extending into said passageway and said locking ring and saidinsert and operative to engage a bone screw extending through saidaperture in said insert.
 20. A fixation instrument for treating a bonefracture as set forth in claim 19 including said aperture extendingthrough said nail member at an angle with respect to the longitudinalaxis of said nail member; and said lower surface extending at an anglesubstantially the same as the angle of said aperture.